In the development process of new energy, as grid-connected generation for the new energy, such as a solar battery, a wind power and a fuel cell, becomes increasingly popular, the technology of grid-connected inverter generation becomes a focus for study.
It has been found by the applicant that, in a practical application, as the number of inverters in a grid-connected generation system increases, generally a resonance occurs in the grid-connected generation system due to the undesirable design of a control circuit and the mutual influence among impedances of control devices, thereby decreasing the opportunity for a safe and reliable operation of the grid-connected generation system.
Therefore, in order to suppress the resonance occurred in the grid-connected generation system, the resonance is generally suppressed using an LCL filter included in the inverter in the conventional technology, for example, with a common active damping suppressing method in the field. However, in the conventional active damping resonance suppressing method, a sample sensor is typically added, and the feasibility and stability are poor. Particularly for a large-scale grid-connected generation system, the generated resonance in the system is generally complicated, the resonance cannot be suppressed using a specific resonance suppressing algorithm, and the resonance even increases due to unsuitable control. Thus such a conventional grid-connected generation system cannot be ensured to operate reliably and stably.